This invention relates, in general, to vehicle linkage systems and, in particular, to a linkage system for use on a vehicle such as earth moving or construction machinery wherein the linkage system is utilized for operating and controlling a loader bucket. More specifically, but without restriction to the particular use which is shown and described, this invention relates to a loader bucket linkage system that is operable to accomplish the function of filling the bucket with material, raising the bucket to a carry position, moving the vehicle to a described located and dumping the material from the bucket at the desired location.
In the operation of contruction machinery vehicles, as is known, linkage systems currently mounted on loader vehicles may include a pair of lift arms pivoted at their ends to the frame of the vheicle and to a lower portion of the bucket, a pair of struts or levers having their intermediate portions pivotally connected to an upper portion of the associated lift arms, a pair of bucket control cylinders having first ends pivotally connected to upper portions of the bucket and second ends pivotally connected to upper ends of associated struts or bucket links, a pair of levers pivotally connected to the frame and to lower ends of associated struts, and a pair of lifting cylinders pivotally connected to the frame and to an intermediate portion of associated arms. There are also used moreover linkage systems which differ from the above in that the intermediate portion of the struts is pivoted to an intermediate portion of the associated arms beneath the pivotal connection of the lifting cylinders. Because of this the struts and the levers are mounted in the space lying between the two arms.
The linkage systems described above have several disadvantages.
In particular, as far as the linkage system first described is concerned, because the lifting cylinders are pivotally connected to the associated arms at a lower portion than the struts, or a lower level thereof, it is necessary to use lifting cylinders of large longitudinal dimensions and therefore of high cost. Moreover, with such an arrangement of lifting cylinders there are greater possibilities for interference with other parts of the machine. If it is desired to reduce the longitudinal dimension of the lifting cylinders and therefore their cost, it is necessary to pivot these latter on a higher lever or an upper portion of the associated arms. But, in order to do this, it is necessary also to shorten the length of the struts and to pivot their intermediate portions on a portion or position of the associated arms nearer to the driver's position with a consequent reduction in the driver's visibility.
Now considering the linkage systems first described, which differ from the preceding ones by the different arrangement of the pivotal connections of the struts and the lifting cylinders on associated lift arms, it is to be noted that with this arrangement the shortening of the lifting cylinders is allowed, but in order to do this it is necessary to place the struts and the levers within the space between the lift arms. This arrangement increases the torsional stresses to which the various constituent parts of the mechanism are subjected and moreover involves an increase in the width of the linkage system or what might be termed the transverse bulk of the linkage system itself.